Ah, nevermind. I see. In the email that Apple generated, there is a 
text/plain part that contains no text, so viewing that part will show 
an empty page.

Send an empty email, see an empty email :)


--Apple-Mail-BA1F88B2-B1C1-4747-87B2-2E8928B3CF18
Content-Type: text/plain;
        charset=us-ascii
Content-Transfer-Encoding: 7bit



--Apple-Mail-BA1F88B2-B1C1-4747-87B2-2E8928B3CF18
Content-Type: text/calendar;
        charset=utf-8;
        name=meeting.ics;
        method=CANCEL
Content-Transfer-Encoding: quoted-printable

.
.
.

Exactly what text are you trying to read?  The ics file should always 
display as an iTip. With the email you forwarded me, I can see the 
text you wrote describing the problem (and I can view it independently 
using the "All Parts" tree. The .ics file, however, doesn't contain 
any viewable text since it's always displayed as the iTip.

Requests:

59.167.157.243 - - [08/Jan/2015:21:50:49 +1000] "GET 
/imp/view.php?actionID=view_attach&id=1&muid=%7B5%7DINBOX76687&view_token=sM1fSkAnJuwM7sCbKk1qnA1&uniq=1420717777212 HTTP/1.1" 200 140 "https://mail.simonandkate.net/imp/dynamic.php?page=mailbox" "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2214.45 
Safari/537.36"0/139729

59.167.157.243 - - [08/Jan/2015:21:50:49 +1000] "GET 
/static/fb85a18e1e69605a98c28e3a610638a1ad7d454b.css HTTP/1.1" 304 - 
"https://mail.simonandkate.net/imp/view.php?actionID=view_attach&id=1&muid=%7B5%7DINBOX76687&view_token=sM1fSkAnJuwM7sCbKk1qnA1&uniq=1420717777212" "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2214.45 
Safari/537.36"0/415

Nothing in Apache error log.

At debug level this is the only Imp reference that I can find:

2015-01-08T21:53:37+10:00 DEBUG: HORDE [imp] Load config file 
(conf.php; app: imp) [pid 1575 on line 109 of 
"/usr/share/pear/Horde/Registry/Loadconfig.php"]
2015-01-08T21:53:38+10:00 DEBUG: HORDE [imp] SQL  (0.0003s)
        SELECT t.field, t.data FROM horde_imap_client_data d INNER JOIN
          horde_imap_client_metadata t ON d.messageid = t.messageid WHERE
          d.hostspec = 'server04.simonandkate.lan' AND d.port = '143' AND
          d.username = 'simon' AND d.mailbox = 'INBOX' AND (t.field =
          'uidvalid') [pid 1575 on line 208 of 
"/usr/share/pear/Horde/Db/Adapter/Pdo/Base.php"]
2015-01-08T21:53:38+10:00 DEBUG: HORDE [imp] SQL  (0.0003s)
        SELECT t.data, t.msguid FROM horde_imap_client_data d INNER JOIN
          horde_imap_client_message t ON d.messageid = t.messageid WHERE
          d.hostspec = 'server04.simonandkate.lan' AND d.port = '143' AND
          d.username = 'simon' AND d.mailbox = 'INBOX' AND (t.msguid = 
'76687') [pid 1575 on line 208 of 
"/usr/share/pear/Horde/Db/Adapter/Pdo/Base.php"]
2015-01-08T21:53:38+10:00 DEBUG: HORDE [imp] Load config file 
(mime_drivers.php; app: horde) [pid 1575 on line 109 of 
"/usr/share/pear/Horde/Registry/Loadconfig.php"]
2015-01-08T21:53:38+10:00 DEBUG: HORDE [imp] Load config file 
(mime_drivers.php; app: imp) [pid 1575 on line 109 of 
"/usr/share/pear/Horde/Registry/Loadconfig.php"]
2015-01-08T21:53:38+10:00 DEBUG: HORDE [imp] Max memory usage: 7864320 
bytes [pid 1575 on line 618 of "/usr/share/pear/Horde/Registry.php"]


Other messages display the text part OK.

Please follow the hints at 
http://wiki.horde.org/FAQ/Admin/Troubleshoot#wsod to generate and find 
a useful error message.

OK, so Imp now reads the ics I sent you and presents me with the ics 
view. It appears to interpret it correctly as a cancellation for the 
1st January cleaning event. Thanks Mike :)

If I go View All Parts, I still cannot view the text at all, Imp just 
shows me an empty screen. Is that to be expected?

IMP 6.2.5

Changes have been made in Git (FRAMEWORK_5_2):

commit 095ab85fbfdba765668d270997db7edcdf80d5f3
Author: Michael J Rubinsky <mrubinsk@horde.org>
Date:   Wed Jan 7 22:10:22 2015 -0500

     Don't ignore components with RECURRENCE-ID attributes if we have 
nothing else.

     The iTip might be a result of an update to an exception etc... Fixes
     Bug: 13777

  imp/lib/Mime/Viewer/Itip.php |   15 ++++++++++++---
  1 files changed, 12 insertions(+), 3 deletions(-)

http://github.com/horde/horde/commit/095ab85fbfdba765668d270997db7edcdf80d5f3

Changes have been made in Git (master):

commit f80ed69a626383450c0db52c9feb46f0eb29e64c
Author: Michael J Rubinsky <mrubinsk@horde.org>
Date:   Wed Jan 7 22:10:22 2015 -0500

     Don't ignore components with RECURRENCE-ID attributes if we have 
nothing else.

     The iTip might be a result of an update to an exception etc... Fixes
     Bug: 13777

  imp/lib/Mime/Viewer/Itip.php |   15 ++++++++++++---
  1 files changed, 12 insertions(+), 3 deletions(-)

http://github.com/horde/horde/commit/f80ed69a626383450c0db52c9feb46f0eb29e64c

As per email discussion:

Quoting Simon Wilson <simon@simonandkate.net>:

This looks like a regression caused by the fix for Bug: 13399. Please
create a ticket on bugs.horde.org to keep this on my radar. You don't
need to upload the ics if it's personal data, as I already have a copy
of it.

--
mike